Hard coating and hard coating-covered member

ABSTRACT

A hard coating, which is to disposed to cover a surface of a tool substrate, has a total thickness of 0.5-20 μm and includes an A layer and nanolayer-alternated layer that are alternately laminated by physical vapor deposition. The nanolayer-alternated layer includes a B layer and C layer that are alternately laminated. The A layer has a thickness of 50-1000 nm and is AlCr(SiC) nitride that is represented by a composition formula of [Al1-W-XCrW(SiC)X]N wherein an atomic ratio W is 0.20-0.80 and an atomic ratio X is 0.01-0.20. The B layer has a thickness of 1-100 nm and is TiAl nitride that is represented by a composition formula of [Ti1-YAlY]N wherein an atomic ratio Y is 0.30-0.85. The C layer has a thickness of 1-100 nm and is Ti(SiC) nitride represented by a composition formula of [Ti1-Z(SiC)Z]N wherein an atomic ratio Z is 0.05-0.45. The nanolayer-alternated layer has a thickness of 50-1000 nm.

TECHNICAL FIELD

The present invention relates to a hard-coating-covered member havingexcellent heat resistance and excellent welding resistance, and moreparticularly to such a hard-coating-covered member excellent in the heatresistance and welding resistance and including an A layer of AlCr(SiC)nitride and a nanolayer-alternated layer which are alternatelylaminated, wherein the nanolayer-alternated layer includes a B layer ofTiAl nitride having a nano-order thickness and a C layer of Ti(SiC)nitride having a nano-order thickness which are alternately laminated.

BACKGROUND ART

Regarding various machining tools such as a cutting tool (e.g., drill,endmill, milling cutter, lathe cutter), a non-cutting tool (e.g.,forming tap, rolling tool, press die) and also various tool members suchas a friction part requiring wear resistance, there is proposed atechnique of covering a surface of a substrate made of cemented carbideor high-speed tool steel, with a hard coating, for improving the wearresistance and durability.

On the other hand, in each of Patent Document 1 and Non-Patent Document1, there is suggested a drill with a hard coating of TiAlN system/TiCrNsystem. In Patent Document 2, there is suggested a drill with a hardcoating constituted by a multilayered structure of AlCrN system andTiSiN system.

PRIOR ART DOCUMENT Patent Documents

[Patent Document 1] WO2013/000557

[Patent Document 2] JP2008-534297A

Non-Patent Documents

[Non-Patent Document 1] “Mechanical properties and failure models ofTiAl(Si)N single and multilayer thin films” (authors: O. Durdnd-Drouhin,A. E. Santana, A. Karimi, V. H. Derflinger, A. Schutze) on pages 260-266of “Surface and Coatings Technology” (Switzerland) Volumes 163-164,published by Elsevier Science in 2003

DISCLOSURE OF THE INVENTION Object to be Achieved by the Invention

However, the drill described in each of the Patent Document 1 andNon-Patent Document 1 had a problem that the drill does not sufficientlyprovide wear resistance when being used to drill carbon steel or castiron. The drill described in Patent Document 2 had a problem that thedrill does not exhibit a sufficient performance when being used to drillalloy steel or stainless steel, since the drill does not sufficientlyprovide welding resistance.

The present invention was made in view of the background discussedabove. It is therefore an object of the present invention to provide ahard-coating-covered tool which provides wear resistance when being usedto cut carbon steel, cast iron or the like, and which provides weldingresistance when being used to cut alloy steel, stainless steel or thelike.

Various studies made by the inventors of the present invention under theabove-described situation revealed a fact that a tool with a hardcoating provides wear resistance when being used to cut carbon steel orcast iron and provides welding resistance when being used to cut alloysteel or stainless steel, wherein the hard coating includes an A layermade of AlCr(SiC) nitride and a nanolayer-alternated layer arealternately arranged to have a total thickness not larger than 20 μm,and wherein the nanolayer-alternated layer includes a B layer made ofTiAl nitride and a C layer made of Ti(SiC) nitride. The presentinvention was made based on the revealed fact.

Measures for Achieving the Object

The essence of the first invention is (a) a hard coating that is to bedisposed to cover a surface of a substrate, wherein (b) the hard coatinghas a total thickness of 0.5-20 μm and includes an A layer and ananolayer-alternated layer that are alternately laminated by physicalvapor deposition, wherein the nanolayer-alternated layer includes a Blayer and a C layer that are alternately laminated, (c) the A layer hasa thickness of 50-1000 nm and is AlCr(SiC) nitride that is representedby a composition formula of [Al_(1-W-X)Cr_(W)(SiC)_(X)]N wherein anatomic ratio W is 0.20-0.80 and an atomic ratio X is 0.01-0.20, (d) theB layer has a thickness of 1-100 nm and is TiAl nitride that isrepresented by a composition formula of [Ti_(1-Y)Al_(Y)]N wherein anatomic ratio Y is 0.30-0.85, (e) the C layer has a thickness of 1-100 nmand is Ti(SiC) nitride that is represented by a composition formula of[Ti_(1-Z)(SiC)_(Z)]N wherein an atomic ratio Z is 0.05-0.45, and (f) thenanolayer-alternated layer has a thickness of 50-1000 nm.

The essence of the second invention is that a ratio T_(A)/T_(NL) of thethickness T_(A) of the A layer to a thickness T_(NL) of thenanolayer-alternated layer is 0.2-10.

The essence of the third invention is that the A layer contains additiveα that is at least one kind of element selected from a group consistingof V, Y, Zr, Nb, Mo, Ta and W, such that a content ratio of the additiveα is not larger than 20 at %.

The essence of the fourth invention is that the B layer containsadditive β that is at least one kind of element selected from a groupconsisting of B, C, V, Cr, Zr, Nb, Mo, Hf, Ta and W, such that a contentratio of the additive β is not larger than 10 at %.

The essence of the fifth invention is that the C layer contains additiveγ that is at least one kind of element selected from a group consistingof B, V, Y, Nb, Mo and W, such that a content ratio of the additive γ isnot larger than 10 at %.

The essence of the sixth invention is that the hard coating is disposedto directly cover the substrate.

The essence of the seventh invention is that the hard coating isdisposed to cover the substrate via an interface layer; and theinterface layer has a thickness of 50-1000 nm, and is made of materialsubstantially the same as material of the A layer, the B layer, the Clayer or the nanolayer-alternated layer.

The essence of the eighth invention is that the substrate is coveredpartially or entirely with the hard coating according to any one of thefirst through seventh inventions.

Effect of the Invention

According to the first invention, the hard coating, which is to becoated on the surface of the substrate, has the total thickness of0.5-20 μm and includes the A layer and the nanolayer-alternated layerthat are alternately laminated by physical vapor deposition, wherein thenanolayer-alternated layer includes the B layer and the C layer that arealternately laminated. The A layer has the thickness of 50-1000 nm andis AlCr(SiC) nitride that is represented by the composition formula of[Al_(1-W-X)Cr_(W)(SiC)_(X)]N wherein the atomic ratio W is 0.20-0.80 andthe atomic ratio X is 0.01-0.20. The B layer has the thickness of 1-100nm and is TiAl nitride that is represented by the composition formula of[Ti_(1-Y)Al_(Y)]N wherein the atomic ratio Y is 0.30-0.85. The C layerhas the thickness of 1-100 nm and is Ti(SiC) nitride that is representedby the composition formula of [Ti_(1-Z)(SiC)_(Z)]N wherein the atomicratio Z is 0.05-0.45. The nanolayer-alternated layer has the thicknessof 50-1000 nm. Thus, crystal grains of each layer are refined, wherebythe coating strength is improved, and excellent oxidation resistance,high hardness and high tenacity are provided. Further, the constructionof alternate lamination of the A layer and the nanolayer-alternatedlayer prevents progress of crack, whereby wear resistance and chippingresistance are improved. Consequently, it is possible to obtain a toolwhich provides wear resistance when being used to cut carbon steel, castiron or the like, and which provides welding resistance when being usedto cut alloy steel, stainless steel or the like.

According to the second invention, the ratio T_(A)/T_(NL) of thethickness T_(A) of the A layer to the thickness T_(NL) of thenanolayer-alternated layer is 0.2-10. Thus, it is possible to obtain atool which provides wear resistance when being used to cut carbon steel,cast iron or the like, and which provides welding resistance when beingused to cut alloy steel, stainless steel or the like.

According to the third invention, the A layer contains the additive αthat is at least one kind of element selected from the group consistingof V, Y, Zr, Nb, Mo, Ta and W, such that the content ratio of theadditive α is not larger than 20 at %. Thus, solid-solutionstrengthening is caused in the A layer whereby the hardness of the Alayer can be increased. Further, since the wear resistance is madeexcellent, the high-temperature strength and high-temperature tenacityare improved and an oxide is formed on the surface by increasedtemperature during a cutting operation, thereby providing excellent wearresistance and preferable balance of wear resistance to weldingresistance, and accordingly resulting in long tool life.

According to the fourth invention, the B layer contains the additive βthat is at least one kind of element selected from the group consistingof B, C, V, Cr, Zr, Nb, Mo, Hf, Ta and W, such that the content ratio ofthe additive β is not larger than 10 at %. Thus, solid-solutionstrengthening is caused in the B layer whereby the hardness of the TiAlnitride can be increased, thereby providing excellent wear resistance.

According to the fifth invention, the C layer contains the additive γthat is at least one kind of element selected from the group consistingof B, V, Y, Nb, Mo and W, such that the content ratio of the additive γis not larger than 10 at %. Thus, solid-solution strengthening is causedin the C layer whereby the hardness of the Ti(SiC) nitride can beincreased, thereby providing excellent wear resistance. Particularly,where the additive γ is at least one of V, Nb, Mo and W, an oxide isformed by increased temperature during a cutting operation, therebyproviding self-lubricating function and accordingly leading to furtherincreased tool life.

According to the sixth invention, the hard coating is disposed todirectly cover the substrate. Thus, an interface layer is not requiredto be disposed between the hard coating and the substrate, whereby theproduction can be made easily.

According to the seventh invention, the hard coating is disposed tocover the substrate via the interface layer, and the interface layer hasthe thickness of 50-1000 nm, and is made of the material substantiallythe same as material of the A layer, the B layer, the C layer or thenanolayer-alternated layer. Thus, it is possible to further increasebonding strength between the heard coating and the substrate.

According to the eighth invention, in the hard-coating-covered tool, thesubstrate is covered partially or entirely with the hard coatingaccording to any one of the first through seventh inventions. Thus, itis possible to obtain a tool which provides wear resistance when beingused to cut carbon steel or cast iron, and which provides weldingresistance when being used to cut alloy steel or stainless steel.

Preferably, the above-described hard-coating-covered tool is used as arotary cutting tool such as drill and milling cutter, a non-rotarycutter such as lathe cutter, a non-cutting tool such as forming tap,rolling tool and press die, and any one of other various kinds ofmachining tools. However, the above-described hard-coating-covered tooldoes not necessarily have to be used as such a machining tool but may beused as any one of various kinds of wear-resistant hard-coating-coveredmember such as bearing member, which requires wear resistance andoxidation resistance.

Further, preferably, the hard coating of the present invention is formedby an arc ion plating, a PVD method such as ion-beam-assisted depositionand sputtering, and other physical vapor deposition.

Further, cemented carbide or high-speed tool steel is preferably used asthe substrate that is to be covered with the hard coating of the presentinvention. However, any one of the other tool materials such as cermet,ceramics, polycrystalline diamond and polycrystalline CBN may be used asthe substrate.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a front view showing a drill provided with a hard coatingaccording to an embodiment of the present invention.

FIG. 2 is an enlarged bottom view as seen from a side of a distal end ofthe drill of FIG. 1, for explaining a construction of the drill.

FIG. 3 is a schematic view of explaining an example of laminatedstructure of the hard coating that is provided to cover the drill ofFIG. 1.

FIG. 4 is a schematic view of explaining another example of laminatedstructure of the hard coating that is provided to cover the drill ofFIG. 1.

FIG. 5 is a schematic view of explaining still another example oflaminated structure of the hard coating that is provided to cover thedrill of FIG. 1.

FIG. 6 is a schematic view of explaining further example of laminatedstructure of the hard coating that is provided to cover the drill ofFIG. 1.

FIG. 7 is a schematic view of explaining an arc ion plating apparatus asan example of a physical vapor deposition apparatus for forming the hardcoating of FIG. 1 on a tool substrate.

FIG. 8 is a table showing kinds of constituent elements of AlCr(SiC)nitride constituting A layers and a ratio of each of the constituentelements in test samples 1-50, which are different in kinds ofconstituent elements and a ratio of each of the constituent elements,kinds and composition ratios of additive and thickness of each of the A,B and C layers constituting the hard coating.

FIG. 9 is a table showing kinds of constituent elements and a ratio ofeach of the constituent elements of TiAl nitride constituting the Blayers in the test samples 1-50 shown in FIG. 8.

FIG. 10 is a table showing kinds of constituent elements and a ratio ofeach of the constituent elements of Ti(SiC) nitride constituting the Clayers in the test samples 1-50 shown in FIG. 8.

FIG. 11 is a table showing the thickness of each of the A layers, Blayers and C layers, a number of pairs of the laminated B layers and Clayers, a thickness of each of nanolayer-alternated layers, a thicknessof an interface layer, a number of pairs of the laminated A layers andnanolayer-alternated layers, and a total thickness of the hard coatingin the test samples 1-50 shown in FIG. 8.

FIG. 12 is a table showing a coating hardness, a wear width, a cuttingdistance and a judgement result in the test samples 1-50 shown in FIG.8.

FIG. 13 is a view showing characteristics of increase of the wear width,which was caused with increase of the cutting distance in the testsamples 2, 3, 12, 22, 29, 37, 40 and 44 of the test samples 1-50 shownin FIG. 8.

MODES FOR CARRYING OUT THE INVENTION

A hard coating as an embodiment of the present invention will now bedescribed in detail with reference to the drawings.

Embodiment

FIGS. 1 and 2 are views showing a drill 10 as an example of ahard-coating-covered tool or a hard-coating-covered member, which iscovered with a hard coating 24 of the present invention. FIG. 1 is thefront view as seen in a direction perpendicular to an axis O of thedrill 10. FIG. 2 is an enlarged bottom view as seen from a side of adistal end of the drill 10 in which cutting edges 12 are provided. Thisdrill 10 is two-fluted twist drill, and includes a shank 14 and a body16 which are axially contiguous to each other and which are formedintegrally with each other. The body 16 has a pair of flutes 18 each ofwhich is formed in the body 16 to be twisted about the axis O in aclockwise direction. The pair of cutting edges 12 are provided byaxially distal ends of the respective flutes 18. The drill 10 is to berotated in a clockwise direction as seen from a side of the shank 14,such that a workpiece is cut by the cutting edges 12 whereby a hole isformed in the workpiece while chips produced as a result of the cuttingof the workpiece are evacuated from the hole toward the shank 14 via theflutes 18.

A pair of cutting-fluid lead-out holes 22 are provided to longitudinallyextend through from an end face of the shank 14 through the shank 14 andthe body 16, and open in respective flank faces 20 that are contiguousto the respective cutting edges 12 in a distal end of the body 16. InFIG. 1, a shaded area indicates a coated portion that is covered with ahard coating in the form of the hard coating 24. In the presentembodiment, the drill 10 is covered at the body 16 as its part with thehard coating 24. However, the drill 10 may be covered in its entiretywith the hard coating 24.

FIG. 3 is a schematic view showing, in enlargement, a cross section ofthe hard coating 24 of the drill 10. As shown in FIG. 3, the hardcoating 24 is disposed on a tool substrate 30 made of, for example,cemented carbide, via an interface layer 32 that is formed by physicalvapor deposition to have a thickness of about 50-1000 nm. The hardcoating 24 is formed by physical vapor deposition, and is constituted byA layers 34 and nanolayer-alternated layers 40 as multi-layer areas.Each of the A layers 34 is formed to have a thickness of 50-1000 nm.Each of the nanolayer-alternated layers 40 is constituted by B layers 36each having a thickness of 1-100 nm and C layers 38 each having athickness of 1-100 nm. The B layers 36 and the C layers 38 arealternately laminated such that each of the nanolayer-alternated layers40 has a thickness of 50-1000 nm. The A layers 34 and thenanolayer-alternated layers 40 are alternately laminated such that thehard coating 24 has a total thickness of 0.5-20 μm. In the hard coating24 shown in FIG. 3, a lamination number of the A andnanolayer-alternated layers 34, 40 is, for example, an even number, anda lamination number of the B and C layers 36, 38 in each of thenanolayer-alternated layers 40 is, for example, an odd number that isnot smaller than 3.

Each of the A layers 34 has the thickness of 50-1000 nm and is made ofAlCr(SiC) nitride that is represented by a composition formula of[Al_(1-W-X)Cr_(W)(SiC)_(X)]N wherein an atomic ratio W is 0.20-0.80 andan atomic ratio X is 0.01-0.20. The AlCr(SiC) nitride contains additiveα that is constituted by at least one kind of element selected from agroup consisting of V, Y, Zr, Nb, Mo, Ta and W, such that the contentratio of the additive α is not larger than 20 at %. The additive α ischaracterized by causing solid-solution strengthening whereby thehardness of the AlCr(SiC) nitride is increased, and causing a strengthof the AlCr(SiC) nitride to be increased and causing an oxide to beformed on the surface of the AlCr(SiC) nitride by increased temperatureduring a cutting operation, thereby increasing ware resistance.

Each of the B layers 36 has the thickness of 1-100 nm and is made ofTiAl nitride that is represented by a composition formula of[Ti_(1-Y)Al_(Y)]N wherein an atomic ratio Y is 0.30-0.85. Each of the Blayers 36 contains additive β that is constituted by at least one kindof element selected from a group consisting of B, C, V, Cr, Zr, Nb, Mo,Hf, Ta and W, such that the content ratio of the additive β is notlarger than 10 at %. The additive β is characterized by causingsolid-solution strengthening whereby the hardness of the TiAl nitride isincreased, thereby contributing to increase of wear resistance.

Each of the C layers 38 has the thickness of 1-100 nm and is made ofTiSi nitride that is represented by a composition formula of[Ti_(1-Z)(SiC)_(Z)]N wherein an atomic ratio Z is 0.05-0.45. Each of theB layers 36 contains additive γ that is constituted by at least one kindof element selected from a group consisting of B, V, Y, Nb, Mo and W,such that the content ratio of the additive γ is not larger than 10 at%. The additive γ is characterized by causing solid-solutionstrengthening whereby the hardness of the Ti(SiC) nitride is increased,thereby contributing to increase of wear resistance. Further, among theadditive γ, V, Nb, Mo and W cause an oxide to be formed by increasedtemperature during a cutting operation, thereby providingself-lubricating function and accordingly contributing to increase oftool life.

The interface layer 32 is formed by physical vapor deposition similar tothe physical vapor deposition by which the hard coating 24 is formed, soas to have a thickness of 50-1000 nm. The interface layer 32 may be madeof the AlCr(SiC) nitride constituting the A layers 34, the TiAl nitrideconstituting the B layers 36, the Ti(SiC) nitride constituting the Clayers 38, or material (TiAl nitride/Ti(SiC) nitride) of nanolayerlaminated structure substantially the same as the nanolayer-alternatedlayers 40. FIG. 3 shows an example where the interface layer 32 is madeof material substantially the same as the A layers 34, namely, is madeof AlCr(SiC) nitride.

In each of the nanolayer-alternated layers 40, a lamination number ofthe B and C layers 36, 38 may be either an even number or an odd numberthat is not smaller than 3. Further, in each of the nanolayer-alternatedlayers 40, an uppermost layer or a lowermost layer may be either the Blayer 36 or C layer 38. In the hard coating 24, a lamination number ofthe A and nanolayer-alternated layers 34, 40 may be either an evennumber or an odd number that is not smaller than 3. Further, in the hardcoating 24, an uppermost layer or a lowermost layer maybe either the Alayer 34 or nanolayer-alternated layer 40.

FIGS. 4, 5 and 6 show constructions of respective other examples of thehard coating 24. The hard coating 24 of FIG. 4 is different from that ofFIG. 3 in that the lamination number of the A and nanolayer-alternatedlayers 34, 40 is an odd number, in that the lamination number of the Band C layers 36, 38 in each of the nanolayer-alternated layers 40 is anodd number; and in that the interface layer 32 is made of TiAl nitridethat is substantially the same as the material of the B layers 36. Thehard coating 24 of FIG. 5 is different from that of FIG. 3 in that theinterface layer 32 disposed between the tool substrate 30 and the hardcoating 24 is made of material (TiAl nitride/Ti(SiC) nitride) ofnanolayer laminated structure substantially the same as the material ofthe nanolayer-alternated layers 40. The hard coating 24 of FIG. 6 isdifferent from that of FIG. 3 in that the lamination number of the A andnanolayer-alternated layers 34, 40 is an odd number, in that theuppermost layer of the hard coating 24 is constituted by thenanolayer-alternated layer 40, and in that the hard coating 24 isdisposed directly on the tool substrate 30 without via the interfacelayer 32.

FIG. 7 is a schematic construction view (schematic view) of explainingan arc ion plating apparatus 50 that is used for manufacturing the drill10. The arc ion plating apparatus 50 is operated to form the interfacelayer 32, A layers 34, B layers 36 and C layers 38 by an arc ion platingas a kind of physical vapor deposition such that these layers 32, 34,36, 38 are deposited on the tool substrate 30 that has a shapesubstantially the same as the drill 10 shown in FIGS. 1 and 2.

The arc ion plating apparatus 50 includes; for example, a rotary table54 to be driven to be rotated about a rotation axis extendingsubstantially in a vertical direction and to hold a plurality ofworkpieces, i.e., the plurality of tool substrates 30 each of which isnot yet covered with the hard coating 24 and has the cutting edges 12and flutes 18 already formed therein; a bias-voltage power source 56 forapplying a negative bias voltage to the tool substrates 30; a processingvessel in the form of a chamber 58 which accommodates therein the toolsubstrates 30; a heater 59 provided in the chamber 58; a reaction-gassupplying device 60 for supplying a reaction gas into the chamber 58; agas discharging device 62 for discharging a gas from an interior of thechamber 58 by, for example, a vacuum pump so as to reduce a pressure inthe interior of the chamber 58; a first arc power source 64; a secondarc power source 66 and a third arc power source 68. The rotary table 54is a cylindrical-shaped or polygonal-prism-shaped table whose centercorresponds to the above-described rotation axis. The plurality of toolsubstrates 30 are held in an outer peripheral portion of the rotarytable 54 such that each of the tool substrates 30 has an attitude thatcauses its distal end protrudes upwardly. The reaction-gas supplyingdevice 60 is equipped with a tank in which argon gas (Ar) is stored andalso a tank in which nitrogen gas is stored, for supplying the nitrogengas when the interface layer 32, A layers 34, B layers 36 and C layers38 are to be formed.

Each of the first arc power source 64; second arc power source 66 andthird arc power source 68 is configured to selectively energize betweena corresponding one of anodes 72, 76, 80 and a corresponding one ofcathodes in the form of first evaporation source 70, second evaporationsource 74 and third evaporation source 78 that are made of vapordeposition material, with an arc current, thereby selectively causingevaporation material to evaporate from the corresponding one of thefirst evaporation source 70, second evaporation source 74 and thirdevaporation source 78. After having being evaporated, the evaporationmaterial becomes positive ion that is deposited to cover the toolsubstrate 30 to which negative (−) bias voltage is applied. It is setsuch that the first arc power source 64, second arc power source 66 andthird arc power source 68 are selected to evaporate a prescribedcomposition for obtaining each of the interface layer 32, A layers 34, Blayers 36 and C layers 38 The arc current and the bias voltage aredetermined. Further, a coating forming condition such as temperature of400-550° C. and vacuum degree of 2-10 Pa is determined. The thickness ofeach of the interface layer 32, A layers 34, B layers 36 and C layers 38is adjusted by controlling a length of time for the coating formation.

For example, the first evaporation source 70 is constituted by anA-layer evaporation-source material which is AlCr(SiC) nitriderepresented by the composition formula of [Al_(1-W-X)Cr_(W)(SiC)_(X)]Nwherein an atomic ratio W is 0.20-0.80 and an atomic ratio X is0.01-0.20 and which contains the additive α that is at least one kind ofelement selected from the group consisting of V, Y, Zr, Nb, Mo, Ta and Wsuch that the content ratio of the additive α is not larger than 20 at%. The second evaporation source 74 is constituted by a B-layerevaporation-source material which is TiAl nitride represented by thecomposition formula of [Ti_(a-Y)Al_(Y)]N wherein an atomic ratio Y is0.30˜0.85 and which contains the additive β that is at least one kind ofelement selected from a group consisting of B, C, V, Cr, Zr, Nb, Mo, Hf,Ta and W such that the content ratio of the additive β is not largerthan 10 at %. The third evaporation source 78 is constituted by aC-layer evaporation-source material which is Ti(SiC) nitride representedby the composition formula of [Ti_(1-Z)(SiC)_(Z)]N wherein an atomicratio Z is 0.05˜0.45 such that the Ti(SiC) nitride contains the additiveγ that is at least one kind of element selected from a group consistingof B, V, Y, Nb, Mo and W such that the content ratio of the additive γis not larger than 10 at %.

When the interface layer 32 is to be formed on the tool substrate 30,for example, the AlCr(SiC) nitride is evaporated from the firstevaporation source 70 by the first arc power source 64, or the TiAlnitride is evaporated from the second evaporation source 74 by thesecond arc power source 66. When each of the A layers 34 is to be formedon the tool substrate 30, the AlCr(SiC) nitride is evaporated from thefirst evaporation source 70 by the first arc power source 64. When eachof the nanolayer-alternated layers 40 is to be formed on the toolsubstrate 30, terms in which the TiAl nitride is evaporated from thesecond evaporation source 74 by the second arc power source 66 and termsin which the Ti(SiC) nitride is evaporated from the third evaporationsource 78 by the third arc power source 68 are alternately providedwhereby the B layers 36 of nano-order constituted by the TiAl nitrideand the C layers 38 of nano-order constituted by the Ti(SiC) nitride arealternately laminated. With these operations being selectively carriedout, the hard coating 24 shown in FIG. 3 is disposed on the toolsubstrate 30, for example.

For checking wear resistance and welding resistance, the presentinventors prepared 50 kinds of test samples 1-50 in each of which thehard coating 24 shown in FIG. 3 is formed on the tool substrate 30having substantially the same shape as the drill 10 shown in FIGS. 1 and2 and made of cemented carbide, by using the arc ion plating apparatus50 of FIG. 7. The test samples 1-50 are different from one another, asshown in FIGS. 8, 9, 10 and 11, in terms of the composition ratios (at%) and thickness (nm) of the interface layer 32, A layers 34, B layers36 and C layers 38, the number of pairs of the laminated B and C layers36, 38 in each of the nanolayer-alternated layers 40, the thickness ofeach of the nanolayer-alternated layers 40 and the number of pairs ofthe laminated A and nanolayer-alternated layers 34, 40. Then, thepresent inventors measured the coating hardness of each of the testsamples 1-50 in accordance with a coating-hardness (Vickers hardness)measuring method described below, and measured the wear width and thecutting distance when a cutting is made by each of the test samples 1-50in accordance with a cutting test condition, so as to evaluate a cuttingperformance. FIG. 12 shows result of the evaluation. It is noted that aunit of composition values shown in FIGS. 8, 9, and 10 is at % (atomic%).

(Coating-Hardness Measuring Method)

In accordance with Vickers hardness test method (JISG0202, Z2244), theHV value (Vickers hardness) of the hard coating of each of the testsamples 1-50 was measured under a condition indicated by hardness symbolHV0.025.

(Cutting Test Condition)

Workpiece material: SCM440 (30HRC)

Cutting speed: 100 m/min.

Rotating speed: 5305 min⁻¹

Feed rate: 0.18 mm/rev.

Cutting depth: 30 mm (blind hole)

Step feed amount: Non-step feed

Cutting fluid: Water-soluble cutting fluid

(Wear-Width Measuring Method)

The drilling was repeated until the cutting distance of the cuttingedges of the distal end of the drill reached 50 m. Then, when thecutting distance reached 50 m, the wear width of the coating in theflank face in the distal end portion of the drill, namely, the width ofexposure of the substrate in portions adjacent to the cutting edges wasactually measured by using a stereoscopic microscope with scale. Themeasured wear width is shown at *1 in FIG. 12.

(Cutting-Distance Measuring Method and Judging Method)

The cutting distance of the cutting edges of the distal end of the drillwas calculated based on the cutting test condition (rotating speed: 5305min⁻¹, feed rate: 0.18 mm/rev, cutting depth: 30 mm) and the number ofmachined holes (total cutting distance) until the wear width of thedrill reached 0.2 mm. The calculated cutting distance is shown at *2 inFIG. 12. Those having the cutting distance shorter 50 m were judgedunacceptable, and are indicated with “X” mark at *3 in FIG. 12. Thosehaving the cutting distance not shorter 50 m were judged acceptable, andare indicated with “O” mark at *3 in FIG. 12.

As shown in FIG. 12, the coating hardness of the test samples 7-50corresponding to the embodiments of the present invention was 3190-3540(HV0.025), and was higher than 2510 as the largest value of the coatinghardness of the test samples 1-6 according to comparative examples.

Further, as shown in FIG. 12, the test samples 1-6 corresponding to thecomparative examples were judged unacceptable, since the cuttingdistance until the wear width reached 0.2 mm was smaller than 50m as anacceptable minimum value. In the test sample 1, due to absence of the Blayers 36, there are not formed the nanolayer-alternated layers 40 eachof which is an alternated layer of the B and C layers 36, 38, and thethickness of the interface layer 32 is larger than 1000 nm. In the testsample 2, due to absence of the C layers 38, there are not formed thenanolayer-alternated layers 40 each of which is an alternated layer ofthe B and C layers 36, 38, and the thickness T_(A) of each of the Alayers 34 is larger than 1000 nm. In the test sample 3, there are notprovided the A layers 34, the thickness T_(B) of each of the B layers 36and the thickness T_(C) of each of the C layers 38 are larger than 100nm, the thickness of each of the nanolayer-alternated layers 40 islarger than 1000 nm, and the total thickness is larger than 20 μm. Inthe test sample 4, the thickness T_(B) of each of the B layers 36 islarger than 100 nm, the thickness T_(C) of each of the C layers 38 issmaller than 1 nm, and the thickness of the interface layer 32 is largerthan 1000 nm. In the test sample 5, there are not provided the A layers34, the thickness T_(B) of each of the B layers 36 and the thicknessT_(C) of each of the C layers 38 are smaller than 1 nm, the thickness ofeach of the nanolayer-alternated layers 40 is smaller than 50 nm, andthe total thickness is smaller than 0.5 μm. In the test sample 6, thethickness T_(A) of each of the A layers 34 is so small and smaller than50 nm, the thickness T_(B) of each of the B layers 36 and the thicknessT_(C) of each of the C layers 38 are smaller than 1 nm, the thickness ofthe interface layer 32 is smaller than 50 nm, and the total thickness issmaller than 0.5 μm.

However, the test samples 7-50 corresponding to the embodiments of theinvention were judged acceptable, since the cutting distance until thewear width reached 0.2 mm was not smaller than 50 m as the acceptableminimum value. It is noted that substantially the same results as thoseshown in FIG. 12 were obtained also in the drills shown in FIGS. 4-6.That is, substantially the same results as those shown in FIG. 12 wereobtained irrespective of whether the interface layer 32 is present orabsent, irrespective of whether the uppermost layer or lowermost layerof the hard coating 24 is the A layer 34 or nanolayer-alternated layer40, irrespective of whether the lamination number of the hard coating 24is an odd number or an even number, and irrespective of whether thelamination number of each of the nanolayer-alternated layers 40 is anodd number or an even number.

In the test samples 7-50 shown in FIG. 12 and corresponding to theembodiments of the invention, the composition of the A layers 34 is suchthat a content ratio of Al is 20-79 at %, a content ratio of Cr is 78-20at %, and the additive α is constituted by an element or elementsselected from V, Y, Zr, Nb, Mo, Ta and W and a content ratio of theadditive α is 0-20 at %, for example, as shown in the test samples 7 and13 of FIG. 8. That is, the preferable composition of the A layers 34 isAlCr(SiC) nitride represented by the composition formula of[Al_(1-W-X)Cr_(W)(SiC)_(X)]N wherein the atomic ratio W is 0.20-0.80 andthe atomic ratio X is 0.01-0.20. The thickness T_(A) of each of the Alayers 34 is preferably 50-1000 nm, for example, as shown in the testsamples 7 and 11 of FIG. 11.

In the test samples 7-50 shown in FIG. 12 and corresponding to theembodiments of the invention, the composition of the B layers 36 is suchthat a content ratio of Ti is 15-70 at %, a content ratio of Al is 85-30at %, and the additive β is constituted by at least one kind of elementof B, C, V, Cr, Zr, Nb, Mo, Hf, Ta and W and a content ratio of theadditive β is 0-10 at %, for example, as shown in the test samples 7 and13 of FIG. 9. That is, the preferable composition of the B layers 36 isTiAl nitride represented by the composition formula of [Ti_(1-Y)Al_(Y)]Nwherein an atomic ratio Y is 0.30-0.85. The thickness T_(B) of each ofthe B layers 36 is preferably 1-100 nm, for example, as shown in thetest samples 10 and 12 of FIG. 11.

In the test samples 7-50 shown in FIG. 12 and corresponding to theembodiments of the invention, the composition of the C layers 38 is suchthat a content ratio of Ti is 53-94.5 at %, a content ratio of (SiC) is5-45 at %, and the additive γ is constituted by at least one kind ofelement of B, C, V, Y, Nb, Mo and W and a content ratio of the additiveγ is 0-10 at %, for example, as shown in the test samples 12 and 16 ofFIG. 10. That is, the preferable composition of the C layers 38 isTi(SiC) nitride represented by the composition formula of[Ti_(1-Z)(SiC)_(Z)]N wherein the atomic ratio Z is 0.05-0.45. Thethickness T_(C) of each of the C layers 38 is preferably 1-100 nm, forexample, as shown in the test samples 10 and 12 of FIG. 11.

In the test samples 7-50 shown in FIG. 12 and corresponding to theembodiments of the invention, the thickness of each of thenanolayer-alternated layers 40 is 50-1000 nm, for example, as shown inthe test sample 7 and 12 of FIG. 11. Further, a ratio T_(A)/T_(NL) ofthe thickness T_(A) of each of the A layers 34 to the thickness T_(NL)of each of the nanolayer-alternated layers 40 is 0.2-10.

In the test samples 7-50 shown in FIG. 12 and corresponding to theembodiments of the invention, the thickness of the interface layer 32 is50-1000 nm, for example, as shown in the test samples 7 and 11 of FIG.11.

In the test samples 7-50 shown in FIG. 12 and corresponding to theembodiments of the invention, the total thickness (total film thickness)of the hard coating 24 is 0.5-20 μm, for example, as shown in the testsamples 19 and 20 of FIG. 11.

In the test samples 7-50 shown in FIG. 12 and corresponding to theembodiments of the invention, the number of repeat in each of thenanolayer-alternated layers 40 in which the B and C layers 36, 38 arelaminated, i.e., the number of pairs of the laminated B and C layers 36,38 in each of the nanolayer-alternated layers 40 is 2-500, for example,as shown in the test samples 48 and 12. Further, the number of repeat inthe hard coating 24 in which the A and nanolayer-alternated layers 34,40 are laminated, i.e., the number of pairs of the laminated A andnanolayer-alternated layers 34, 40 in the hard coating 24 is 2-199, forexample, as shown in the test samples 7 and 12.

FIG. 13 is a view showing characteristics of increase of the wear width,which was caused with increase of the cutting distance in the testsamples 2 and 3 corresponding to the comparative examples and the testsamples 12, 22, 29, 37, 40 and 44 corresponding to the embodiments ofthe invention in the above-described cutting test. A rate of increase ofthe wear width in the test samples 2 and 3 corresponding to thecomparative examples is considerably large as compared with that in thetest samples 12, 22, 29, 37, 40 and 44 corresponding to the embodimentsof the invention.

According to the present embodiment, the hard coating 24, which is to bedisposed to cover the surface of the tool substrate 30, has the totalthickness of 0.5-20 μm, and consists of the A layers 34 and thenanolayer-alternated layers 40 that are alternately laminated byphysical vapor deposition, wherein each of the nanolayer-alternatedlayers 40 consists of the B layers 36 and the C layers 38 that arealternately laminated. Each of the A layers 34 has the thickness of50-1000 nm and is AlCr(SiC) nitride that is represented by thecomposition formula of [Al_(1-W-X)Cr_(W)(SiC)_(X)]N wherein the atomicratio W is 0.20-0.80 and the atomic ratio X is 0.01-0.20. Each of the Blayers 36 has the thickness of 1-100 nm and is TiAl nitride that isrepresented by the composition formula of [Ti_(1-Y)Al_(Y)]N wherein theatomic ratio Y is 0.30-0.85. Each of the C layers 38 has the thicknessof 1-100 nm and is Ti(SiC) nitride that is represented by thecomposition formula of [Ti_(1-Z)(SiC)_(Z)]N wherein the atomic ratio Zis 0.05-0.45. Each of the nanolayer-alternated layers 40 has thethickness of 50-1000 nm. Consequently, it is possible to obtain thedrill 10 which provides wear resistance when being used to cut carbonsteel, cast iron or the like, and which provides welding resistance whenbeing used to cut alloy steel, stainless steel or the like.

According to the present embodiment, the ratio T_(A)/T_(NL) of thethickness T_(A) of each of A layers 34 to the thickness T_(NL) of eachof the nanolayer-alternated layers 40 is 0.2-10. Thus, it is possible toobtain a tool which provides wear resistance when being used to cutcarbon steel, cast iron or the like, and which provides weldingresistance when being used to cut alloy steel, stainless steel or thelike.

According to the present embodiment, each of the A layers 34 containsthe additive α that is at least one kind of element selected from thegroup consisting of V, Y, Zr, Nb, Mo, Ta and W, such that the contentratio of the additive α is not larger than 20 at %. Thus, solid-solutionstrengthening is caused in each of the A layers 34 whereby the hardnessof the AlCr(SiC) nitride can be increased, so that the strength isincreased and an oxide is formed on the surface by increased temperatureduring a cutting operation, thereby providing excellent wear resistanceand preferable balance of wear resistance to welding resistance, andaccordingly resulting in long tool life of the drill 10.

According to the present embodiment, each of the B layers 36 containsthe additive β that is at least one kind of element selected from thegroup consisting of B, C, V, Cr, Zr, Nb, Mo, Hf, Ta and W, such that thecontent ratio of the additive β is not larger than 10 at %. Thus,solid-solution strengthening is caused in each of the B layers 36whereby the hardness of the TiAl nitride can be increased, therebyproviding excellent wear resistance of the drill 10.

According to the present embodiment, each of the C layers 38 containsthe additive γ that is at least one kind of element selected from thegroup consisting of B, V, Y, Nb, Mo and W, such that the content ratioof the additive γ is not larger than 10 at %. Thus, solid-solutionstrengthening is caused in each of the C layers 38 whereby the hardnessof the Ti(SiC) nitride can be increased, thereby providing excellentwear resistance of the drill 10. Particularly, where the additive γ isat least one of V, Nb, Mo and W, an oxide is formed by increasedtemperature during a cutting operation, thereby providingself-lubricating function and accordingly leading to further increasedtool life of the drill 10.

According to the present embodiment, the hard coating 24 shown in FIG. 6is disposed to directly cover the tool substrate 30. Thus, an interfacelayer is not required to be disposed between the hard coating 24 and thetool substrate 30, whereby the production can be made easily.

According to the present embodiment, the hard coating 24 shown in FIGS.3, 4 and 5 is disposed to cover the tool substrate 30 via the interfacelayer 32, and the interface layer 32 has the thickness of 50-1000 nm,and is made of the material substantially the same as material of the Alayers 34, B layers 36 or nanolayer-alternated layers 40. Thus, it ispossible to further increase bonding strength between the heard coating24 and the tool substrate 30.

According to the present embodiment, the drill 10 is ahard-coating-covered tool is covered partially with the hard coating 24.Thus, it is possible to provide wear resistance when the drill 10 isused to cut carbon steel or cast iron, and provide welding resistancewhen the drill 10 is used to cut alloy steel or stainless steel.

While the embodiment of the present invention has been described indetail by reference to the accompanying drawings, it is to be understoodthat the described embodiment is merely an embodied form and that thepresent invention can be embodied with various modifications andimprovements on the basis of knowledge of those skilled in the art.

DESCRIPTION OF REFERENCE SIGNS

10: Drill (Hard-coating-covered tool, Hard-coating-covered member), 30:Tool substrate (substrate), 24: Hard coating, 34: A layers, 36: Blayers, 38: C layers, 40: nanolayer-alternated layers

The invention claimed is:
 1. A hard coating that is to be disposed tocover a surface of a substrate, wherein the hard coating has a totalthickness of 0.5-20 μm and includes an A layer and ananolayer-alternated layer that are alternately laminated by physicalvapor deposition, the nanolayer-alternated layer including a B layer anda C layer that are alternately laminated, the A layer has a thickness of50-1000 nm and is AlCr(SiC) nitride that is represented by a compositionformula of [Al_(1-W-X)Cr_(W)(SiC)_(X)]N wherein an atomic ratio W is0.20-0.80 and an atomic ratio X is 0.01-0.20, the B layer has athickness of 1-100 nm and is TiAl nitride that is represented by acomposition formula of [Ti_(1-Y)Al_(Y)]N wherein an atomic ratio Y is0.30-0.85, the C layer has a thickness of 1-100 nm and is Ti(SiC)nitride that is represented by a composition formula of[Ti_(1-Z)(SiC)_(Z)]N wherein an atomic ratio Z is 0.05-0.45, and thenanolayer-alternated layer has a thickness of 50-1000 nm.
 2. The hardcoating according to claim 1, wherein a ratio T_(A)/T_(NL) of thethickness T_(A) of the A layer to a thickness T_(NL) of thenanolayer-alternated layer is 0.2-10.
 3. The hard coating according toclaim 1, wherein the A layer contains additive α that is at least onekind of element selected from a group consisting of V, Y, Zr, Nb, Mo, Taand W, such that a content ratio of the additive α is not larger than 20at %.
 4. The hard coating according to claim 1, wherein the B layercontains additive β that is at least one kind of element selected from agroup consisting of B, C, V, Cr, Zr, Nb, Mo, Hf, Ta and W, such that acontent ratio of the additive β is not larger than 10 at %.
 5. The hardcoating according to claim 1, wherein the C layer contains additive γthat is at least one kind of element selected from a group consisting ofB, V, Y, Nb, Mo and W, such that a content ratio of the additive γ isnot larger than 10 at %.
 6. The hard coating according to claim 1,wherein the hard coating is disposed to directly cover the substrate. 7.The hard coating according to claim 1, wherein the hard coating isdisposed to cover the substrate via an interface layer, and theinterface layer has a thickness of 50-1000 nm, and is made of materialsubstantially the same as material of the A layer, the B layer or thenanolayer-alternated layer.
 8. A hard-coating-covered member comprisingthe substrate is covered partially or entirely with the hard coatingaccording to claim
 1. 9. The hard coating according to claim 1, whereinthe A layer and the B layer are the AlCr(SiC) nitride and the TiAlnitride, respectively, which are represented by the respectivecomposition formulas that are different from each other, and aredifferent from each other in terms of main constituent elements.
 10. Thehard coating according to claim 1, wherein one of the A layer, the Blayer and the C layer constitutes an uppermost layer of the hardcoating.
 11. The hard coating according to claim 1, wherein the A layercontains additive α that is at least one kind of element selected fromthe group consisting of V, Y, Zr, Nb, Mo, Ta, and W, such that a contentratio of the additive α is not larger than 20 at %, the B layer containsadditive β that is at least one kind of element selected from a groupconsisting of B, C, V, Cr, Zr, Nb, Mo, Hf, Ta, and W, such that acontent ratio of the additive β is not larger than 10 at %, and the Clayer contains additive γ that is at least one kind of element selectedfrom a group consisting of B, V, Y, Nb, Mo, and W, such that a contentratio of the additive γ is not larger than 10 at %.